It has long been recognized that it is desirable to restrict uncontrolled lateral swaying between a towing vehicle and an articulated trailer. Several anti-sway mechanisms have been developed for this purpose. One such mechanism is disclosed in Sanders U.S. Pat. No. 3,787,077 and operates on a principle which is similar to that of many commercially available anti-sway mechanisms. In the Sanders anti-sway mechanism, a front member is connected at its forward end to the towing vehicle to pivot about an axis which is offset laterally from the hitch axis. The front member is telescoped frictionally with a rear member which is pivotally connected to the trailer. When the trailer tends to sway, a frictional retarding force is created between the two telescoped members and serves to restrict the swaying motion.
Difficulty has been encountered in using anti-sway mechanisms with trailers which are equipped with certain types of surge brake actuators such as, for example, the actuator disclosed in Huetsch et al U.S. Pat. No. 4,223,766 entitled Trailer Hitch and Brake Actuating Assembly. That actuator includes a front unit which is pivotally connected to the hitch ball on the towing vehicle and which is movably interconnected with a rear unit adapted to be carried on the trailer. When the trailer surges forwardly, the rear unit moves forwardly relative to the front unit and causes the actuator to automatically apply the trailer brakes.
If a conventional anti-sway mechanism is used with a trailer which is equipped with a surge brake actuator, the anti-sway mechanism renders the brake actuator virtually inoperable. That is to say, the same frictional force which is created by the anti-sway mechanism to restrict sway also acts to retard forward surging of the trailer. Thus, the rear unit of the actuator is prevented from moving forwardly in normal fashion relative to the front unit and hence the trailer brakes cannot be applied under normal surge conditions.
The problem of using an anti-sway mechanism with a surge brake actuator has been recognized. In order to overcome this problem, some manufacturers of anti-sway mechanisms have provided mounting adaptors which enable the anti-sway mechanism to be used without impairing the action of the brake actuator. Such adaptors, however, can be used only with certain types of actuators and are entirely unsuitable for use with actuators of the type disclosed in the aforementioned Huetsch et al patent.